Pressure fluid operated drill motor



Aug. 28, 1962 P. A. LINCOLN PRESSURE: FLUID OPERATED DRILL MOTOR Filed March 28, 1960 mvENToR PAUL A. LlNcL/V le IW S B ul" L 2 4 /C 6. F s 4 /r f VIN; L 7 J Lo 3 United States Patent Rand Company, New York, NX., a corporation of New Jersey Filed Mar. 2S, 1960, Ser. No. 18,063 9 Clmms. (Cl. 121-15) This invention relates to pressure fluid operated motors particularly adapted for use in pneumatically operated drills of the percussive type such as are used in rock drilling and similar operations.

The invention is particularly adapted to those applications where the diameter of the drill -body is limited as for instance in those cases where the drill is adapted to follow the drill bit down the drill hole. In such cases of course, the diameter of the drill is circumscribed by the diameter of the drill bit and it must be somewhat smaller, not only to get into the drill hole, but to permit the escape of the drill cuttings.

Generally speaking, this condition limits the capacity of the actuating motor, it being understood that the air pressures usually available are not often above nominally one hundred pounds per square inch as hose and various accessories are ordinarily designed for such pressures.

One of the great advantages of using a drill which follows the bit down the drill hole is that the length of the bit and its tail portion, which is ordinarily struck by a hammer piston within the drill, can be short. -lt has been found to be of advantage if the hammer piston is approximately the length of the bit. Vibrations set up in the bit and piston react most favorably in this state of affairs whereby the greatest amount of energy is transmittable to the face of the rock for breaking it. In the past, various arrangements of tandem cylinders have been suggested, but this has the effect of lengthening the striking element and the consequent setting up of vibrations within the piston, causing fractures in the material of which they are made.

lIn accordance with the practice of this invention use is made of an auxiliary piston of shorter stroke than the main striking piston so that the assistance which it affords, while available to accelerate the piston, ceases before a blow is struck on the drill bit. Such an arrangement has other advantages in that the auxiliary piston is provided with means for controlling the exhaust from the main cylinder which occurs at the time of separation of the auxiliary piston from the main piston. On the recovery stroke of the main piston, relatively little retardation is produced by the auxiliary piston as the main piston picks it up since means is provided to assist in this, and, furthermore, as the main piston rejoins the auxiliary piston it is not traveling at a lvery high speed so that the blow therebetween is relatively light.

It is accordingly an object of this invention to provide a drill motor of the type described which is powerful, of small lateral dimension, and having the advantages of a tandem arrangement of pistons, without the disadvantages which have been inherent in such designs.

Other objects and advantages of the construction Will be in part pointed out, and in part obvious hereinafter in the description of a preferred embodiment illustrated in the drawing, in which yFIGURE 1 is a longitudinal section of the rear part of a drill motor as applied to a rock drill;

FIG. 2 is a continuation of the forward part of the drill shown in FIG. 1 and shows the end of the main piston, its housing, and the drill bit which it is adapted to strike; and

FIG. 3 is a cross sectional view of the drill at the line 3--3 of FIG. l looking in the direction of the arrows.

Referring to the drawing, there is shown a rock drill provided with an elongated housing for the drill motor Patented Aug. 28, 1962 which is adapted to actuate percussively a drill bit 12. Slnce the housing 10 is adapted to follow drill bit 12 into the hole being drilled, it is of appreciably smaller diameter than that bit. The extreme rear portion of the housing and its contents are not shown as they have no special signicance in connection with the description of this invention. It will suflice to say that pressure uid for motivating the drill enters the motor at a central space 14 and from there passes through various parts of the motor. A back head 22 for cylinder 16 is provided, and houses an oscillating valve 24 of well known construction, controlling a port 26 leading to the rear end of cylinder 16, and a port 28 communicating with the front end of cylinder d6. For this purpose port 28 registers with a port 30 in the side of cylinder 16 leading to a groove 32 cut lengthwise of the housing 10 and communicating with a groove 34 cut lengthwise in the wall of cylinder 16 to lead to a port 36 at the front of cylinder 16.

Thus, as the valve 24 oscillates, it is adapted to feed motive air alternately to the front and back ends of cylinder 16, causing piston 18 to reciprocate within cylinder 16, and to deliver blows to the tail portion 20 of bit 12.

As thus far described the motor, piston 18, and bit 12 are of a well known type. The exhaust from the rear end of the cylinder escapes by way `of a conduit 38, in this instance, formed axially in piston118 and extending axially thereof to communicate with a similar bore 40 in bit 12, escaping into the bore hole at the end of the bit as shown at `42. The exhaust from the front end of the cylinder escapes by way of flutes 44 cut in the nose of piston 18, so that as piston 18 withdraws into the cylinder the flutes are uncovered by a front cylinder washer 46 to permit the exhausting air to enter into the interior of the chuck sleeve `48 which, as shown at 50, is iluted to engage corresponding utes 60' on the tail portion 20 of bit 12.

This invention provides means for accelerating piston 18 on its downward stroke by force additional to that exerted by the air within cylinder 16. To this end, a second or auxiliary cylinder 62 is provided, titting within housing 10, lcoaxially with cylinder 16, within which is adapted to reciprocate a second or auxiliary piston 64 having a nose portion 66 extending through the Ifront end 68 of cylinder 62 into the rear end of cylinder 16. To avoid interference with the action of valve 24 through which the nose or plunger 66 passes, a stationary 'bearing sleeve 70 is provided in a bore 72 formed in back head 22, and fitting a similar bore 74 in the front end of cylinder `62. Bushing 70 ts nose 66 rather closely and prevents any substantial leakage between the front end of cylinder 62 and the back end of cylinder 16. The back end of cylinder 62 is provided with a constant supply of pressure fluid by way of an `opening 76 which provides constant communication between the space 14 and the interior of the cylinder 62. A port 7S in the side of cylinder 62 communicating with a space 80 between the cylinder 62 and the outer housing 10 also provides the means `of conducting motive uid to valve 24 by Way of a longitudinal port S2 in the lfront end of cylinder 62. Motive fluid for operating the piston 64 in a backward direction is supplied from the groove 32 in the outer housing 10 which registers with a port 84 leading to a bore 86 in the front end of cylinder 62.

The bore 86 is smaller than lthe main diameter of the cylinder 62 for the purpose `of forming a` `dead air packet at 88 in the front of cylinder 62 which prevents slamming of the piston 64 onto its seat. Accordingly, piston 64 is in the form of a stepped piston, it having a smaller diameter as at 90 to fit the reduced bore 86.

As will be noted in FIG. 1, piston 64 has a shorter stroke than piston 18. Accordingly, as piston 64 advances, the nose 66 leaves piston 18 at the forward part of the stroke of the latter piston. This feature aiiords the use of nose `66 of piston 64 as a valve to control exhaust conduit 38 and is therefore provided with a valve-like tapered face 92 to cooperate with a seat 94 formed at the entrance to conduit 38. Thus, Vas the two pistons 64 and 18 move forward, for the greater part of the stroke of piston 18, exhaust conduit 38 is closed, but opens when auxiliary piston 64 has reached the end of its stroke. The momentum of piston 18, however, carries it forward to strikerthe end `of bit 12, even though the exhaust passage 38 is open.

It will be noted that an additional port 96 is provided in the wall of cylinder 16 which ordinarily will not be opened as piston 18 does not uncover it. However, when the ldrill is pulled back to remove it from the drill hole, bit 12 is `able to slide forward which will permit piston 18 also to slide forward and to cover front supply port 36 so that normally the drill would stop since piston 18 then would have no air supplied yto its forward face to return it. In such position, port 96 is uncovered and consequently, regardless of Whatever position valve 24 may be in, air under pressure will be fed into the back end of cylinder 16 and down through the exhaust port to provide ex-tra blowing to remove cuttings from the hole.

Usually the holes being drilled are quite deep and require a great deal of compressed air to blow cuttings out.v

If the exhaust air is insuilcient for this purpose at great depths of hole, additional supply of air can be provided through an axial bore 98 somewhat restricted but permitting the flow of a considerable volume of air through piston 64 -and into the exhaust passage 38. This will supplement, of course, the exhaust air from the tool.

`Motors of this sort lare subject to a great ydeal of vibration Iand it is desirable that they should be provided with a certain amount of cushioning of the parts to relieve severe shocks. For this purpose, the rear cylinder is held in place by a heavy coil spring 99 which presses against head 100 of cylinder 62 which, in turn, presses against the cylinder back head 22, cylinder 16, front cylinder washer 46 and chuck sleeve 48.

The chuck may be of any desired form. In this instance, however, the chuck sleeve 48 is =a plain sleeve which contacts with splines 102 on the tail end 20 of bit 12. Sleeve 48 is held in place by a nut 104, screwed into the forward end of housing pressing against keys 106 interposed between it and chuck sleeve 48. Splines 102 on tail part 20 of the bit are discontinuous as to provide considerable endwise motion of the bit, being limited in this motion by the keys 106. Rotation of bit 12 is prevented by splines 108 cooperating with splines 102 on the bit.

In operation, the motor is lowered into the drill hole and the various parts are soon to be in the position shown 1n the drawings except that bit 12 would have dropped forward and piston 18 likewise dropped yforward coveringY supply port 36 and opening porty 96. Air being turned on, would pass from the space 14 through port 78, passage 80 to valve 24 and being open to the'front supply port 28 would pass through port 30, passageway 34, port 96, down through the exhaust passage 38, and out through the end of the bit at 42, blowing suciently into the hole to clean the bottom face. Y

As soon as the drill, however, reaches bottom with the bit 12 on the rock face, piston 18 is pushed back to is being 'built up in the back end of cylinder 16 which is transmitted into the port 26. Thus, in the well known manner of operation of such valves, valve 24 rocks to admit air under pressure into the port 26 to start reverse reciprocation of piston 18.

Simultaneously, air under pressure is permitted to eS- cape from the forward end of cylinder 62 via ports 84 and port 36 causing an increase of unbalanced pressure on auxiliary piston 64. This gives great increase in force to push piston 18 forward until piston 64 reaches the end of its stroke, it being cushioned at the air pocket 88 as ther-reduced,portion` of piston `64 'enters bore 86. At' this point, the two valving surfaces 92 and 94 separate to, exhaustair throughconduit 38. The consequent re-V duction in pressure in cylinder -16 and passages 26 rocks valve 24 to the position to close that port. Meanwhile, the nose of piston 18 strikes its lblow on the tail portion 20 of bit 12 and the reaction in the opposite `direction starts as above described.

, The disconnection of piston 64 from piston 18 has a great advantage in that vibrational shocks set up in piston 18 will not be transmitted to auxiliary piston 64. Due to this separation, the force of the blow of the piston is much greater on bit 12 than it would otherwise be. As could be shown by a theoretical analysis if piston 64 remained in contact with piston .18, the reaction of the blow on bit 12 would be such as to throw piston 64 backward, probably destroying the surfaces at which piston 64 contacts piston 18. There is, of course, the additional advantage in the use of the nose portion 66 as a valve to control the exhaust to the drill hole.

Thus by the above construction are accomplished, among others, the objects hereinbefore referred to.

I claim:

l. A motor for pressure fluid actuated rock drills having a main cylinder, a main piston reciprocatory in said cylinder having its power stroke in a forward direction and a recovery stroke in the opposite direction, a valve automatically operable to control the flow of motive pressure fluid to the cylinder for actuating the main piston, an auxiliary cylinder, an `auxiliary piston in said auxiliary cylinder having a shorter stroke than said main piston, a plunger for said auxiliary piston and extending therefrom to Contact said main piston and to transmit driving force thereto, said yauxiliaryV cylinder being rearwardly open constantly to full fluid pressure to urge said auxiliary piston forward and having conduit means forward of the auxiliary piston associated with said valve for intermittent admission of pressure fluid to said auxiliary cylinder.

2. A drill motor as set forth in claim l in which the main piston is provided with an axial bore therethrough n terminating in a Valve seat, and said plunger is provided with a seat to seal the bore at said valve seat.

3. A drill motor as set forth in claim 1 in which the main piston is provided with an axial bore therethrough terminating in a valve seat, and said plunger is provided Y with a seat to intermittently seal the bore at said valve the position shown in FIG. lwhereupon air entering at Y port 36 pushes the piston back so that the nose 66 of auxiliary piston 64 closes exhaust passage 38 at the two seats 92 and 94 whereupon the two pistons rise. Some of the force of the air `at the top of piston 64 is counterbalanced by air admitted through ports 84 to the forward Y.

end of the cylinder 62. Upwardmotion of the two pistons 18 and V64 continues until the nose of piston 18 is withdrawn into the cylinder which allows air to escape from the forward end of the cylinder past the flutes 44 into the exhaust bore 40 in the bit reducing the pressure under the face of valve 24. At the same time, pressure seat and is additionally provided with a restricted axial bore for the transmission of pressure fluid to the main piston bore from the rearward end of the auxiliary cylinder.

4. A pressure fluid operated drill motor comprising, a cylinder, a first pressure fluid actuated piston reciprocatory in said cylinder, a valve adapted to control admission of pressure uid to said cylinder to actuate said first piston in a working stroke, a second cylinder coaxial with the first cylinder, a second piston pressure fluid actuated to advance in said second cylinder, a plunger on said second piston extending into the first cylinder to abuttingly contact said rst piston for conjoined movement with the latter for a substantial part Vof the Working stroke of the first piston to accelerate the rst pistonV during its working stroke, and an exhaust conduit for said lirst cylinder, said plunger being arranged to control access to said exhaust conduit.

5. A pressure uid operated drill motor comprising, -a cylinder, a irst pressure fluid actuated piston disposed for reciprocation within said cylinder, a valve constructed and `arranged to control admission of pressure fluid to said cylinder from a source of pressure fluid, said iirst piston having a pressure surface exposed to said fluid admitted into said cylinder for driving said rst piston in a working stroke, an exhaust passage in said rst piston, a second cylinder coaxial with the rst cylinder, a second pressure fluid actuated piston disposed for reciprocation in said second cylinder and having a pressure surface exposed to pressure fluid from said source thereof to accelerate said second piston in a working stroke, a plunger on said second piston extending into the rst cylinder to abuttingly contact said iirst piston for conjoined movement with the latter to seal said exhaust passage for a substantial part of the working stroke of the latter, said pressure surface of the second piston having an area greater than the area of said exhaust passage so that the second piston on its Working stroke when the plunger abuttingly contacts the first piston accelerates the latter during -a substantial part of the working stroke of said iirst piston.

6. A drill motor as set forth in claim 5 in which the exhaust conduit is disposed in the irst piston.

7. The drill motor as defined in claim 5 wherein the exhaust conduit extends longitudinally of the said rst piston and is covered by the end of said plunger when the latter abuttingly contacts said rst piston.

8. The drill motor of claim 5 in which the iirst piston after its power stroke returns the plunger and the second piston to its initial starting position for another power stroke.

9. A pressure iluid operated drill motor comprising, a cylinder, a piston reciprocatory in said cylinder, a valve adapted to control admission of pressure iluid to said cylinder, a second cylinder coaxial with the said rst cylinder, a second piston pressure fluid actuated to advance in said second cylinder, a plunger on said second piston extending into the first cylinder to connect with said rst piston for part of the working stroke of the rst piston 'and thereby urge the latter forward, an exhaust conduit for the said rst cylinder, said plunger being arranged to control access to said exhaust conduit, and means controlled by said valve to admit pressure fluid to said second cylinder to at least partially counterbalance the pressures on said second piston.

References Cited in the tile of this patent UNITED STATES PATENTS 2,580,203 Topanelian Dec. 25, 1951 2,661,928 Topanelian Dec. 8, 1953 2,800,884 Mori June 30, 1957 2,810,549 Morrison Oct. 22, 1957 2,851,251 Mori Sept. 9, 1958 2,917,025 Dulaney Dec. 15, 1959 2,943,603 Bassinger Iuly 5, 1960 2,947,519 Feucht Aug. 2, 1960 2,979,033 Bassinger Apr. 11, 1961 

